On 11/07/2018 08:37, Chris Hogg wrote:
On Wed, 11 Jul 2018 08:21:38 +0100, Jeff Layman
wrote:
I believe that what you require is a "latching relay".
Latching or non-latching? I thought the latter, i.e. didn't stay
latched on when the power failed, but ICBW and probably am!
Should really be 'latching while power remains applied', if we're being
pedantic.
The act of pressing a momentary push-button causes the relay to pull in,
and an extra set of contacts on the relay are wired across the
push-button (so the effect is the same as if the push-button was kept
depressed - so long as there is power on the relay.
If/when the power feeding the relay is interrupted, then the relay drops
out, and won't pull in again until the push-button is manually depressed.
https://www.eleinmec.com/figures/024_03.gif for the schematic, or for
chapter & verse.